Substrates with transferable chiplets

ABSTRACT

A method for fabricating a substrate having transferable chiplets includes forming a photo-sensitive adhesive layer on a process side of a source substrate including active components or on a patterned side of a transparent intermediate substrate. The intermediate substrate is brought into contact with the source substrate to adhere the active components on the process side to the patterned side of the intermediate substrate via the photo-sensitive adhesive layer therebetween. Portions of the source substrate opposite the process side thereof are removed to singulate the active components. Portions of the photo-sensitive adhesive layer are selectively exposed to electromagnetic radiation through the intermediate substrate to alter an adhesive strength thereof. Portions of the photo-sensitive adhesive layer having a weaker adhesive strength are selectively removed to define breakable tethers comprising portions of the adhesive layer having a stronger adhesive strength. The breakable tethers physically secure the active components to the intermediate substrate.

CLAIM OF PRIORITY

The present application claims priority under 35 USC §119 to U.S.Provisional Patent Application Ser. No. 61/494,507 entitled “Substrateswith Transferable Chiplets,” filed on Jun. 8, 2011, the disclosure ofwhich is incorporated by reference herein in its entirety.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is related to U.S. Provisional PatentApplication Ser. No. 61/494,514 entitled “Methods for Surface Attachmentof Flipped Active Components,” filed on Jun. 8, 2011, the disclosure ofwhich is incorporated by reference herein in its entirety.

FIELD

The present invention is directed to methods for providing substrateshaving separate electrically active components distributed thereon andrelated devices.

BACKGROUND

Substrates with electronically active components distributed over theextent of the substrate may be used in a variety of electronic systems,for example flat-panel imaging devices such as flat-panel liquid crystalor organic light emitting diode (OLED) display devices. Substrates withelectrically active components are also found in flat-panel solar cells.A variety of methods may be used to distribute electronically activecircuits over substrates, including forming the electronically activecircuits on a substrate and forming the components on separatesubstrates and placing them on a substrate. In the latter case, avariety of assembly technologies for device packaging may be used.

Electronically active components made in place are typically formed bysputtering a layer of inorganic semiconductor material or byspin-coating organic material over the entire substrate. Inorganicsemiconductor materials can be processed to improve their electroniccharacteristics, for example amorphous silicon can be treated to formlow-temperature or high-temperature poly-crystalline silicon. In otherprocess methods, microcrystalline semiconductor layers can be formed byusing an underlying seeding layer. These methods typically improve theelectron mobility of the semiconductor layer. The substrate and layer ofsemiconductor material can be photo-lithographically processed to defineelectronically active components, such as transistors. Such transistorsare known as thin-film transistors (TFTs) since they are formed in athin layer of semiconductor material, typically silicon. Transistors mayalso be formed in thin layers of organic materials. In these devices,the substrate is often made of glass, for example Corning Eagle® orJade® glass designed for display applications.

The above techniques may have some limitations. Despite processingmethods used to improve the performance of thin-film transistors, suchtransistors may provide performance that is lower than the performanceof other integrated circuits formed in mono-crystalline semiconductormaterial. Semiconductor material and active components can be providedonly on portions of the substrate, leading to wasted material andincreased material and processing costs. The choice of substratematerials may also be limited by the processing steps necessary toprocess the semiconductor material and the photo-lithographic steps usedto pattern the active components. For example, plastic substrates have alimited chemical and heat tolerance and do not readily survivephoto-lithographic processing. Furthermore, the manufacturing equipmentused to process large substrates with thin-film circuitry is relativelyexpensive. Other substrate materials that may be used include quartz,for example for integrated circuits using silicon-on-insulatorstructures as described in U.S. Patent Application 2010/0289115 and U.S.Patent Application 2010/0123134. However, such substrate materials canbe more expensive and/or difficult to process.

Other methods used for distributing electronically functional componentsover a substrate in the circuit board assembly industry include, forexample, pick-and-place technologies for integrated circuits provided ina variety of packages, for example, pin-grid arrays, ball-grid arrays,and flip-chips. However, these techniques may be limited in the size ofthe integrated circuits that can be placed.

In further manufacturing techniques, a mono-crystalline semiconductorwafer is employed as the substrate. While this approach can providesubstrates with the same performance as integrated circuits, the size ofsuch substrates may be limited, for example, to a 12-inch diametercircle, and the wafers are relatively expensive compared to othersubstrate materials such as glass, polymer, or quartz.

In yet another approach, thin layers of semiconductor are bonded to asubstrate and then processed. Such a method is known assemiconductor-on-glass or silicon-on-glass (SOG) and is described, forexample, in U.S. Pat. No. 7,605,053, issued Oct. 20, 2009. If thesemiconductor material is crystalline, high-performance thin-filmcircuits can be obtained. However, the bonding technique and theprocessing equipment for the substrates to form the thin-film activecomponents on large substrates can be relatively expensive.

Publication No. 11-142878 of the Patent Abstracts of Japan entitled“Formation of Display Transistor Array Panel” describes etching asubstrate to remove it from a thin-film transistor array on which theTFT array was formed. TFT circuits formed on a first substrate can betransferred to a second substrate by adhering the first substrate andthe TFTs to the surface of the second substrate and then etching awaythe first substrate, leaving the TFTs bonded to the second substrate.This method may require etching a significant quantity of material, andmay risk damaging the exposed TFT array.

Other methods of locating material on a substrate are described in U.S.Pat. No. 7,127,810. In this approach, a first substrate carries athin-film object to be transferred to a second substrate. An adhesive isapplied to the object to be transferred or to the second substrate inthe desired location of the object. The substrates are aligned andbrought into contact. A laser beam irradiates the object to abrade thetransferring thin film so that the transferring thin film adheres to thesecond substrate. The first and second substrates are separated, peelingthe film in the abraded areas from the first substrate and transferringit to the second substrate. In one embodiment, a plurality of objects isselectively transferred by employing a plurality of laser beams toabrade selected area. Objects to be transferred can include thin-filmcircuits.

U.S. Pat. No. 6,969,624 describes a method of transferring a device froma first substrate onto a holding substrate by selectively irradiating aninterface with an energy beam. The interface is located between a devicefor transfer and the first substrate and includes a material thatgenerates ablation upon irradiation, thereby releasing the device fromthe substrate. For example, a light-emitting device (LED) is made of anitride semiconductor on a sapphire substrate. The energy beam isdirected to the interface between the sapphire substrate and the nitridesemiconductor releasing the LED and allowing the LED to adhere to aholding substrate coated with an adhesive. The adhesive is then cured.These methods, however, require the patterned deposition of adhesive onthe object(s) or on the second substrate. Moreover, the laser beam thatirradiates the object may need to be shaped to match the shape of theobject and the laser abrasion can damage the object to be transferred.Furthermore, the adhesive cure takes time, which may reduce thethroughput of the manufacturing system.

Another method for transferring active components from one substrate toanother is described in “AMOLED Displays using Transfer-PrintedIntegrated Circuits” published in the Proceedings of the 2009 Societyfor Information Display International Symposium Jun. 2-5, 2009, in SanAntonio Tex., US, vol. 40, Book 2, ISSN 0009-0966X, paper 63.2 p. 947.In this approach, small integrated circuits are formed over a buriedoxide layer in a crystalline wafer. The small integrated circuits arereleased from the wafer by etching the buried oxide layer formed beneaththe circuits. A PDMS stamp is pressed against the wafer and the circuitsare adhered to the stamp. The circuits are pressed against a destinationsubstrate coated with an adhesive and thereby adhered to the destinationsubstrate. The adhesive is subsequently cured. This method, however, mayrely on non-standard and relatively more expensive integrated circuitprocesses that may increase costs associated with, for example, theformation of the buried oxide layer.

SUMMARY

It should be appreciated that this Summary is provided to introduce aselection of concepts in a simplified form, the concepts being furtherdescribed below in the Detailed Description. This Summary is notintended to identify key features or essential features of thisdisclosure, nor is it intended to limit the scope of the disclosure.

According to some aspects of the present invention, in a method ofprinting transferable components, a photo-sensitive adhesive layer isformed on a process side of a source substrate including activecomponents or on a patterned side of a transparent intermediatesubstrate. The transparent intermediate substrate is contacted with thesource substrate to adhere the active components on the process side tothe patterned side of the transparent intermediate substrate via thephoto-sensitive adhesive layer therebetween. Portions of the sourcesubstrate opposite the process side are removed to singulate the activecomponents. Portions of the photo-sensitive adhesive layer areselectively exposed to electromagnetic radiation through the transparentintermediate substrate to alter an adhesive strength thereof, and thenportions of the photo-sensitive adhesive layer having a weaker adhesivestrength are selectively removed to define breakable tethers comprisingportions of the adhesive layer having a stronger adhesive strength. Thebreakable tethers physically secure the active components to thetransparent intermediate substrate.

In some embodiments, in selectively exposing portions of thephoto-sensitive adhesive layer, a mask pattern may be formed on thetransparent intermediate substrate, and the transparent intermediatesubstrate including the mask pattern thereon may be exposed to theelectromagnetic radiation. The mask pattern may include a materialconfigured to block transmission of the electromagnetic radiationtherethrough such that the portions of the photo-sensitive adhesivelayer exposed by the mask pattern are selectively exposed to theelectromagnetic radiation.

In some embodiments, the patterned side of the transparent intermediatesubstrate may include a plurality of structures protruding therefrom,and the mask pattern may be formed on surfaces of the protrudingstructures.

In some embodiments, the tethers may extend in a direction perpendicularto the transparent intermediate layer and may be shaped to break in adesired manner.

In some embodiments, the active components may have respective primarysurfaces including conductive elements thereon adjacent the process sideof the source substrate, and respective secondary surfaces opposite theprimary surfaces. The portions of the adhesive layer defining thetethers may physically connect the respective the primary surfaces ofthe active components to the transparent intermediate substrate.

In some embodiments, a stamp having pillars protruding therefrom may bepressed against the active components on the transparent intermediatesubstrate, and then the stamp may be separated from the transparentintermediate substrate to break the tethers and adhere the respectivesecondary surfaces of the active components to respective transfersurfaces of the pillars of the stamp. The stamp including the activecomponents on the pillars thereof may be contacted with a destinationsubstrate to adhere the respective primary surfaces of the activecomponents including the conductive elements thereon to a receivingsurface of the destination substrate.

In some embodiments, the conductive elements on the respective primarysurfaces of the active components may be adhered to respectiveelectrical contacts on the receiving surface of the destinationsubstrate.

In some embodiments, the primary surfaces of the active components mayrespectively include a photo-adhesive layer residue thereon includingrespective portions of the breakable tethers. The residue may be belowrespective surfaces of the conductive elements.

In some embodiments, the portions of the photo-sensitive adhesive layermay be selectively exposed to the electromagnetic radiation todifferentially adhere ones of the active components to the transparentintermediate substrate.

According to further aspects of the present invention, an activecomponent array includes at least one printable electronic componentincluding a conductive element on a primary surface thereof. Theconductive element is configured to provide an electrical coupling to atleast one active element on the primary surface. The at least oneelectronic component includes a photo-adhesive layer residue on theprimary surface thereof. The residue includes a broken portion of atether configured to adhere the at least one electronic component to atransparent intermediate substrate. The photo-adhesive layer residueincludes a material configured to provide altered adhesive strengthresponsive to exposure to electromagnetic radiation. The activecomponent array further includes destination substrate including one ormore electrical contacts on a surface thereof. The at least oneelectronic component is printed on the destination substrate such thatthe conductive element on the primary surface thereof is in contact witha respective one of the electrical contacts on the receiving surface ofthe destination substrate.

According to one aspect of the present invention, a method forfabricating a substrate having transferable chiplets comprises:providing a source substrate having a process side and a plurality ofactive components formed on or in the process side of the sourcesubstrate; providing a transparent intermediate substrate having apatterned side; coating a photo-sensitive adhesive layer on thepatterned side of the transparent intermediate wafer or on the activecomponents; adhering the patterned side of the transparent intermediatesubstrate to the process side of the source substrate; removing portionsof the source substrate to singulate the active components and adherethe singulated active components to the patterned side of thetransparent intermediate substrate; selectively exposing thephoto-sensitive adhesive layer to electromagnetic radiation to alter anadhesive strength thereof such that portions of the photo-sensitiveadhesive layer have a weaker adhesive strength than other portionsthereof; and selectively removing the portions of the photo-sensitiveadhesive layer having the weaker adhesive strength to define breakabletethers comprising the other portions of the photo-sensitive adhesivelayer that physically connect the singulated active components to thetransparent intermediate substrate.

According to another aspect of the present invention, a transfer device,comprises: a transparent intermediate substrate having a patterned side;a patterned photo-sensitive adhesive layer adhered to the patterned sideof the transparent intermediate substrate, the patterned adhesive layercomprising a material configured to provide altered adhesive strengthresponsive to exposure to electromagnetic radiation; and a plurality ofsingulated active components adhered to the patterned adhesive layer,the patterned adhesive layer located between the patterned side of thetransparent intermediate substrate and the singulated active components,the patterned adhesive layer forming tethers physically connecting thesingulated active components to the patterned side of the transparentintermediate substrate.

Embodiments of the present invention provide transferablehigh-performance active components that can be assembled onto substratesusing standard integrated circuit processes at a reduced cost.

Other methods and/or devices according to some embodiments will becomeapparent to one with skill in the art upon review of the followingdrawings and detailed description. It is intended that all suchadditional embodiments, in addition to any and all combinations of theabove embodiments, be included within this description, be within thescope of the invention, and be protected by the accompanying claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-section of a source substrate having activecomponents on a process side in accordance with embodiments of thepresent invention;

FIG. 2A is a schematic of a transparent intermediate substrate having anoptical mask in accordance with embodiments of the present invention;

FIG. 2B is a schematic cross-section of a transparent intermediatesubstrate having a structured surface and an optical mask in accordancewith embodiments of the present invention;

FIG. 3 is a schematic cross-section of a transparent intermediatesubstrate having an optical mask and a coated photo-sensitive adhesivelayer in accordance with embodiments of the present invention;

FIG. 4 is a schematic cross-section of a transparent intermediatesubstrate adhered to a source substrate in accordance with embodimentsof the present invention;

FIG. 5 is a schematic cross-section of active components adhered to thetransparent intermediate substrate after removing most of the sourcesubstrate in accordance with embodiments of the present invention;

FIG. 6 is a schematic cross-section of active components adhered to thetransparent intermediate substrate after patterning and etching thesource substrate in accordance with embodiments of the presentinvention;

FIG. 7A is a schematic cross-section illustrating the patterned exposureof a photo-sensitive adhesive layer through an optical mask on thetransparent intermediate substrate in accordance with embodiments of thepresent invention;

FIG. 7B is a schematic cross-section illustrating the patterned exposureof a photo-sensitive adhesive layer using a patterned laser beam inaccordance with embodiments of the present invention;

FIG. 8A is a schematic cross-section of a source substrate having activecomponents pattern-wise adhered to the transparent intermediatesubstrate in accordance with embodiments of the present invention;

FIG. 8B is a schematic bottom view of the structure of FIG. 8A.

FIG. 9A is a schematic cross-section of a source substrate having activecomponents pattern-wise adhered to the transparent intermediatesubstrate according to some embodiments of the present invention;

FIG. 9B is a schematic bottom view of the structure of FIG. 9A.

FIG. 9C is a schematic cross-section of the structure of FIG. 9A havingconductive material on the connection pads according to anotherembodiment of the present invention;

FIG. 9D is a schematic cross-section of the structure of FIG. 9A havingshaped tethers according to another embodiment of the present invention;

FIG. 9E is a schematic cross-section illustrating particulatecontamination from fractured tethers according to another embodiment ofthe present invention;

FIG. 10 is a schematic cross-section of a stamp having a pattern ofpillars in accordance with embodiments of the present invention;

FIG. 11 is a schematic cross-section of a stamp having a pattern ofpillars pressed against active components adhered to the transparentintermediate substrate in accordance with embodiments of the presentinvention;

FIG. 12 is a schematic cross-section of active components adhered to thestamp pillars with broken tethers on the transparent intermediatesubstrate in accordance with embodiments of the present invention;

FIG. 13 is a schematic cross-section of active components adhered to thestamp pillars in accordance with embodiments of the present invention;

FIG. 14 is a schematic cross-section of active components adhered to thestamp pillars and pressed against the receiving side of the destinationsubstrate in accordance with embodiments of the present invention;

FIG. 15 is a schematic cross-section of active components adhered to thereceiving side of the destination substrate in accordance withembodiments of the present invention;

FIG. 16 is a flow diagram illustrating a method in accordance withembodiments of the present invention;

FIG. 17 is a flow diagram illustrating another method in accordance withembodiments of the present invention;

FIG. 18 is a flow diagram illustrating a further method in accordancewith embodiments of the present invention;

FIG. 19 is a flow diagram illustrating yet another method in accordancewith embodiments of the present invention; and

FIG. 20 is a flow diagram illustrating a method in accordance withembodiments of the present invention.

The figures are not drawn to scale since the individual elements of thedrawings have too great a size variation to permit depiction to scale.

DETAILED DESCRIPTION OF EMBODIMENTS

The present invention now will be described more fully hereinafter withreference to the accompanying drawings, in which embodiments of theinvention are shown. However, this invention should not be construed aslimited to the embodiments set forth herein. Rather, these embodimentsare provided so that this disclosure will be thorough and complete, andwill fully convey the scope of the invention to those skilled in theart. In the drawings, the thickness of layers and regions areexaggerated for clarity. Like numbers refer to like elements throughout.

It will be understood that when an element such as a layer, region orsubstrate is referred to as being “on” or extending “onto” anotherelement, it can be directly on or extend directly onto the other elementor intervening elements may also be present. In contrast, when anelement is referred to as being “directly on” or extending “directlyonto” another element, there are no intervening elements present. Itwill also be understood that when an element is referred to as being “incontact with” or “connected to” or “coupled to” another element, it canbe directly contacting or connected to or coupled to the other elementor intervening elements may be present. In contrast, when an element isreferred to as being “in direct contact with” or “directly connected to”or “directly coupled to” another element, there are no interveningelements present.

It will also be understood that, although the terms first, second, etc.may be used herein to describe various elements, these elements shouldnot be limited by these terms. These terms are only used to distinguishone element from another. For example, a first element could be termed asecond element, and, similarly, a second element could be termed a firstelement, without departing from the scope of the present invention.

Furthermore, relative terms, such as “under” or “lower” or “bottom,” and“over” or “upper” or “top,” may be used herein to describe one element'srelationship to another element as illustrated in the Figures. It willbe understood that relative terms are intended to encompass differentorientations of the device in addition to the orientation depicted inthe Figures. For example, if the device in one of the figures is turnedover, elements described as being on the “lower” side of other elementswould then be oriented on “upper” sides of the other elements. Theexemplary term “lower”, can therefore, encompasses both an orientationof “lower” and “upper,” depending of the particular orientation of thefigure. Similarly, if the device in one of the figures is turned over,elements described as “below” or “beneath” other elements would then beoriented “above” the other elements. The exemplary terms “below” or“beneath” can, therefore, encompass both an orientation of above andbelow.

The terminology used in the description of the invention herein is forthe purpose of describing particular embodiments only and is notintended to be limiting of the invention. As used in the description ofthe invention and the appended claims, the singular forms “a”, “an” and“the” are intended to include the plural forms as well, unless thecontext clearly indicates otherwise. It will also be understood that theterm “and/or” as used herein refers to and encompasses any and allpossible combinations of one or more of the associated listed items. Itwill be further understood that the terms “comprises” and/or“comprising,” when used in this specification, specify the presence ofstated features, integers, steps, operations, elements, and/orcomponents, but do not preclude the presence or addition of one or moreother features, integers, steps, operations, elements, components,and/or groups thereof.

Embodiments of the invention are described herein with reference tocross-section illustrations that are schematic illustrations ofidealized embodiments (and intermediate structures) of the invention. Assuch, variations from the shapes of the illustrations as a result, forexample, of manufacturing techniques and/or tolerances, are to beexpected. Thus, embodiments of the invention should not be construed aslimited to the particular shapes of regions illustrated herein but areto include deviations in shapes that result, for example, frommanufacturing. In other words, the regions illustrated in the figuresare schematic in nature and their shapes are not intended to illustratethe actual shape of a region of a device and are not intended to limitthe scope of the invention.

Unless otherwise defined, all terms used in disclosing embodiments ofthe invention, including technical and scientific terms, have the samemeaning as commonly understood by one of ordinary skill in the art towhich this invention belongs, and are not necessarily limited to thespecific definitions known at the time of the present invention beingdescribed. Accordingly, these terms can include equivalent terms thatare created after such time. It will be further understood that terms,such as those defined in commonly used dictionaries, should beinterpreted as having a meaning that is consistent with their meaning inthe present specification and in the context of the relevant art andwill not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein. All publications, patent applications,patents, and other references mentioned herein are incorporated byreference in their entireties.

Embodiments of the present invention provide methods and devices for thetransfer of active components, also referred to herein as ‘chiplets,’from a source substrate to a destination substrate. Chiplets are smallintegrated circuits, each integrated circuit having a separate anddistinct substrate so as to define a separate transferable component.FIGS. 1-15 are schematic diagrams illustrating various fabricationoperations in various methods according to embodiments of the presentinvention, while FIGS. 16-20 are flow diagrams describing variousfabrication operations in various methods according to embodiments ofthe present invention. Transferring integrated circuits from the sourcesubstrate to the destination substrate is also referred to herein as‘printing’ the integrated circuits onto the destination substrate.

Referring to the flow diagram of FIG. 16 and to the illustration of FIG.1, some embodiments of the present invention provide a method forfabricating a substrate having transferable chiplets. A source substrate20 having a process side 24 is provided in step 100. The sourcesubstrate 20 can be a wafer having a process side 24 opposite a backside that is used to handle and transport the wafer. Active components22, also referred to herein as ‘chiplets,’ are formed on or in theprocess side 24 of the source substrate 20 and connection pads 26providing electrical connectivity to the active components 22 are formedon or in the active components 22. The source substrate 20 can be asemiconductor wafer, for example, a silicon or gallium arsenide wafer.The source substrate 20 can be an inert substrate, for example glass,with semiconductor layers formed on or over the inert substrate. Thesource substrate 20 can have an inert layer (e.g. silicon dioxide) withsemiconductor layers formed on or over the inert layer. Semiconductorlayers can include crystalline, microcrystalline, polycrystalline, oramorphous materials, according to various embodiments of the presentinvention.

According to some embodiments of the present invention as shown in FIG.16, the source substrate 20 can be provided with active components 22and connection pads 26 already formed on the process side 24.Alternatively, as shown in FIG. 17, an unprocessed source substrate 20can be provided in step 101 and the active components 22 formed on theprocess side 24 of the source substrate 20 in step 102. According toFIG. 17, an unprocessed source substrate 20 is a substrate that has notyet been processed to form the active components 22. The unprocessedsource substrate 20 can have other processing steps completed, forexample cleaning, deposition of material layers, or heat or chemicaltreatments, as are used in the photo-lithographic arts. In step 102,active components 22 are formed, for example using photo-lithographicprocesses including forming masks over the source substrate 20, etchingmaterials, removing masks, and depositing materials. Using suchprocesses, active components 22 are formed on or in the process side 24of the source substrate 20. Source substrate trenches or wells 21 areoptionally formed between the active components 22 to assist insingulating the active components 22 from the source substrate 20 asdescribed further below.

Active components 22 are small electronic integrated circuits, orchiplets, having a size (for example) of about 5 microns to about 5000microns in a dimension. The electronic integrated circuits can includesemiconductor materials (for example, inorganic materials such assilicon or gallium arsenide, or organic materials) having variousstructures, including crystalline, microcrystalline, polycrystalline, oramorphous structures. The active components 22 can also includeinsulating layers and structures such as silicon dioxide, nitride, andpassivation layers, and conductive layers or structures including wiresmade of aluminum, titanium, silver, copper, tungsten, or gold, which canform an electronic circuit. Connection pads 26 can be formed of metalssuch as aluminum, copper, tin, polysilicon semiconductors, or otherinterconnection materials used in the integrated circuit packagingindustry and can be provided on the top surface of the active components22. These and other methods and materials used in the integrated circuitarts may be used for making active component 22 electronic circuits.Large numbers of such small integrated circuits are formed on a singlesource substrate 20. The active components 22 are typically packed asclosely as possible to use the surface area of the source substrate 20as efficiently as possible.

As shown in FIG. 2A, a transparent intermediate substrate 80 is providedin step 105 (FIG. 16). A transparent intermediate substrate 80 may bepart of a transfer device 5 (as shown in FIG. 9) formed in accordancewith embodiments of the present invention using a substrate or wafer toremove active components 22 from the source substrate 20. Thetransparent intermediate substrate 80 is transparent to one or moreselected types of electromagnetic radiation, for example light,ultra-violet radiation, or infra-red radiation. The transparentintermediate substrate 80 need not be transparent to all frequencies ofelectromagnetic radiation nor is it completely transparent, for exampleit can absorb radiation at all frequencies. For example, the transparentintermediate substrate 80 can be partially transparent and absorb 50% ofthe electromagnetic radiation that passes through. However, thetransparent intermediate substrate 80 is sufficiently transparent toselected frequencies of electromagnetic radiation to adequately exposedesired photo-sensitive materials through the transparent intermediatesubstrate 80. In various embodiments of the present invention, thetransparent intermediate substrate 80 can include a glass substrate or aquartz wafer.

An additional or alternative structure is illustrated in FIG. 2B, wherethe patterned side 84 of the transparent intermediate substrate 80 caninclude a structured surface as well as the optical mask 82 onprotruding portions of the structured surface. Such a structured surfacecan serve to increase the distance between portions of the transparentintermediate substrate 80 and the active components 22. The increaseddistance between the transparent intermediate substrate 80 from theactive components 22 except in the areas of the optical mask 82 canimprove the removal of material between the transparent intermediatesubstrate 80 and the active components 22, as discussed further belowwith respect to step 120.

Referring to FIGS. 2A, 2B, and 16, the transparent intermediatesubstrate 80 can include a patterned optical mask 82 formed on apatterned side 84 of the transparent intermediate substrate 80. Thetransparent intermediate substrate 80 can be provided with a patternedoptical mask 82 already formed on the patterned side 84. Alternatively,as shown in FIG. 18, an unprocessed transparent intermediate substrate80 is provided (step 106) and the optical mask 82 is formed from a metallayer or other material opaque to the selected frequencies ofelectro-magnetic radiation using conventional photo-lithographicprocesses (step 107). The optical mask 82 is used to selectively provideelectro-magnetic radiation to portions of a photo-sensitive material, asillustrated in FIG. 7A. In other embodiments of the present invention,the transparent intermediate substrate 80 does not include a patternedoptical mask 82, and another method is used to selectively provideelectro-magnetic radiation to portions of a photo-sensitive material, asshown for example in FIG. 7B.

Referring to FIGS. 3 and 16, a photo-sensitive adhesive layer 30 iscoated on the patterned side 84 of the transparent intermediatesubstrate 80 in step 110. The photo-sensitive adhesive layer 30 can alsobe formed on the active components 22 on the source substrate 20, or onboth the transparent intermediate wafer 80 and the active components 22.The photo-sensitive adhesive layer 30 can be a photo-sensitive polymeror resin, as are commercially available. In some embodiments, thephoto-sensitive adhesive layer 30 can be pattern-wise exposed toelectromagnetic radiation to form a stronger adhesive bond in desiredareas when developed. In some embodiment, the photo-sensitive adhesivelayer 30 can be heat sensitive to cure the photo-sensitive adhesivematerial. Both positive- and negative-acting photo-sensitive materialscan be used in embodiments of the present invention. However, asdescribed below by way of example, a material that is cured to form astronger bond (for example with heat) and then pattern-wise exposed toelectromagnetic radiation to weaken the bond in desired areas isemployed. In other embodiments, a material that is pattern-wise exposedto form a stronger bond in desired areas can be employed. Positive- andnegative-acting pattern-wise bonding processes may be used to achievethese effects.

The photo-sensitive adhesive can be coated as a layer on the patternedside 84 of the transparent intermediate substrate 80 or the activecomponents 22 in various ways, for example by spin or curtain coating orby applying the photo-sensitive material from an adhesive carrier. Inembodiments of the present invention, coating the photo-sensitivematerial as a layer does not limit the methods used to form thephoto-sensitive adhesive layer 30 and simply refers to any method ortechnique employed to form a layer 30 of photo-sensitive adhesive on thepatterned side 84.

As shown in FIG. 4 and referenced in FIG. 16, once the photo-sensitiveadhesive layer 30 is applied to the patterned side 84 of the transparentintermediate substrate 80 or the active components 22, the process side24 of the source substrate 20 is brought into contact with thephoto-sensitive adhesive layer 30 and adhered in step 115. If theoptical mask 82 is present on the transparent intermediate substrate 80,the optical mask 82 is aligned with the active components 22 on thesource substrate 20. The active components 22 and the connection pads 26are in contact with the photo-sensitive adhesive layer 30. Thephoto-sensitive adhesive layer 30 can then be cured to a desired bondingor adhesive strength, for example with heat or by waiting the desiredlength of time, or both. In some embodiments, the photo-sensitiveadhesive layer 30 can be patterned and developed before or after thesource substrate 20 is brought into contact with the photo-sensitiveadhesive layer 30.

Referring to FIG. 5 and step 120 of FIG. 16, portions of the sourcesubstrate 20 are removed except for the active components 22. Forexample the back side of the source substrate 20 opposite the processside 24 can be removed together with any portions of the sourcesubstrate 20 that are not part of the active components 22, leaving thesingulated active components 22 adhered to the transparent intermediatewafer 80. The active components 22 are singulated by the removal step sothat they have independent, separate substrates and do not share asubstrate with any other active component 22. As shown in FIGS. 5 and 6,this can be accomplished in two different steps, first removing amajority of the source substrate 20 and secondly removing a remainingminority of the source substrate 20. For example, the majority of thesource substrate 20 can be removed by a thinning process such asback-side grinding the source substrate 20 up to the active components22. Back-side grinding is a process used in the photo-lithographic orsemiconductor arts. Once the bulk of the source substrate 20 is removed,the source substrate portions 20A between the active components 22 canbe etched away, for example by forming a mask over the active components22 and employing an etchant, as shown in FIG. 6. Alternatively, if thetrenches or wells 21 (FIG. 1) are formed in the source substrate 20, thestep of back-side grinding the source substrate 20 can render additionalsource substrate removal steps unnecessary, if enough material isremoved to reach the substrate trenches or wells 21 to thereby singulatethe active components 22.

In another embodiment of the present invention, the photo-sensitiveadhesive layer 30 can be patterned and developed before or after thesource substrate 20 is reduced, or between the first removal step andthe second removal step. In yet another embodiment, the majority of thesource substrate 20 can be removed before the source substrate 20 isadhered to the transparent intermediate substrate 80. Thus, variousembodiments of the present invention can employ various ordering of thesource substrate 20 removal steps (step 120), the adhesive layer coatingstep (110), or the patterning step (125).

A structured surface on the transparent intermediate substrate (as shownin FIG. 2B) can ease or improve the removal of the source substratematerial. Furthermore, the presence of the protruding structures on thepatterned side 24 of the transparent intermediate substrate 80′ can leadto a thinner tether and improve the tether break. The materials in thesource substrate portions 20A can include layers and materials, forexample dielectric materials, deposited over the source substrate 20process side 24 to form the active components; these layers andmaterials in the source substrate portions 20A are removed. Masking andetching processes are used in the integrated circuit arts and anycombination of these techniques can be employed and are included inembodiments of the present invention. For example, the entire sourcesubstrate 20 (exclusive of the active components 22) can be removed bymasking and etching.

After the removal of the source substrate 20 (leaving the activecomponents 22 adhered to the transparent intermediate substrate 80), thephoto-sensitive adhesive layer 30 is exposed as illustrated in FIG. 7Aor 7B and referenced in step 125 of FIG. 16. Note that the order of theexposure and removal steps 125, 120 can be interchanged, depending onthe strength of the adhesive bond and the type or technique used forsource substrate material removal. For example, the photo-sensitiveadhesive layer 30 could be only lightly cured as adequate for asubsequent source substrate 20 grind or etch process step, and thenexposed. Thus positive- or negative-acting photo-sensitive adhesivematerials can be used to form the adhesive layer 30 in variousembodiments of the present invention.

Referring to FIG. 7A, a blanket exposure of radiation 40 is providedthrough the transparent intermediate substrate 80 onto thephoto-sensitive adhesive layer 30. The optical mask 82 on the patternedside 84 prevents exposure in undesired areas of the photo-sensitiveadhesive layer 30. Alternatively, as shown in FIG. 7B, a selective orpatterned exposure of electromagnetic radiation is provided in alignmentwith the source substrate 20 to expose the desired portions of thephoto-sensitive adhesive layer 30 only, for example by using one or morelaser beams to sequentially expose the desired portions. Masks externalto the transparent intermediate substrate 80 can also be employed. Inboth the embodiment of FIG. 7A and the embodiment of FIG. 7B, thepatterned electro-magnetic radiation exposure provides differentialbonding strength in the photo-sensitive adhesive layer 30 to formtethers connecting the active components 22 to the transparentintermediate substrate 80 as shown in FIG. 8A. In FIG. 8A, darker andlighter portions illustrate the differentially exposed portions of thepatterned photo-sensitive adhesive layer 32. FIG. 8B shows the activecomponents 22 and the differentially exposed patterned photo-sensitiveadhesive layer 32 with a schematic bottom-view.

Referring to FIG. 9A and as referenced in step 130 of FIG. 16, theportions of the patterned photo-sensitive adhesive layer 32 that do notform the tethers 60 are removed, for example by washing with a suitableliquid. Washing adhesive materials as part of a mask formation processis a technique used in the photo-lithographic arts. FIG. 9B shows theactive components 22, the differentially exposed layer patternedphoto-sensitive adhesive 32, and the tethers 60 with a schematicbottom-view.

The tethers 60 formed in the patterned photo-sensitive adhesive layer 32and shown in FIG. 9A serve to physically connect the active components22 to the patterned side 84 of the transparent intermediate substrate80. The tethers 60 can be relatively small and thin, to readily enableremoval of the active components 22 from the transparent intermediatesubstrate 80 by breaking the tethers 60 as described further below. Invarious embodiments of the present invention, the active components 22have various numbers of individual tethers 60. Alternatively, a singletether 60 can be connected to multiple active components 20. The numberand location of tethers 60 connecting the active components 22 to thetransparent intermediate substrate 80 are a matter of design choice. Thetethers 60 are formed in a layer between the active components 22 andthe transparent intermediate substrate 80. The active components 22 andthe transparent intermediate substrate 80 also form layers so that theactive components 22, the transparent intermediate substrate 80, and thetethers 60 are all in different layers so that the tethers 60 form abridge between the active component layer and the transparentintermediate substrate layer and extend in a direction perpendicular tothe layers.

Referring to FIG. 9C, various conductive or adhesive materials 28 can becoated or placed on the connection pads 26 prior to pressing the stamp90 against the active components 22 (step 145). Such materials caninclude materials intended to promote adhesion between the activecomponents and other substrates (as described further below), forexample materials such as solder or tin or to promote conduction. Thedeposition of such materials (e.g. solder balls) is used in the art.

Referring to FIG. 9D, the tethers 60 can be shaped using variousprocessing techniques, such as chemical etching or laser ablation priorto pressing the stamp 90 against the active components 22 (step 145).Such shaping can enhance the transfer of active components 22 to thestamp 90 described below with reference to FIG. 10 by improvingcharacteristics associated with breaking the tethers 60. For example,the tethers 60 can be shaped to improve their predictability inbreaking, reduce the force required to break the tethers 60, control thelocation of the breaks, reduce the number of particulates generated bythe breaks, and/or control the location of particulates generated by thebreak. Referring to FIG. 9E for example, a tether break can becontrolled so that any fracture residue is below the bonding surface ofthe connection pad 26. Thus, any particulates 64 generated from thefracture are not located on the surface of the connection pads 26 and donot interfere with conductivity and/or adhesion to the surface of theconnection pad 26.

Thus, FIGS. 9A, 9B, 9C, and 9D illustrate various transfer devices 5 ofthe present invention. In some embodiments of the present invention, thetransfer device 5 comprises a transparent intermediate substrate 80having a patterned side 84, a patterned photo-sensitive adhesive layer32 adhered to the patterned side 84 of the transparent intermediatesubstrate 80, and a plurality of singulated active components 22 adheredto the patterned photo-sensitive adhesive layer 32. The patternedphoto-sensitive adhesive layer 32 is located between the patterned side84 of the transparent intermediate substrate 80 and the singulatedactive components 22. The patterned photo-sensitive adhesive layer 32forms tethers 60 physically connecting the active components 22 to thepatterned side 84 of the transparent intermediate substrate 80responsive to exposure to electromagnetic radiation. The transfer device5 can included an optical mask 82 formed on the patterned side 84 of thetransparent intermediate substrate 80. The patterned photo-sensitiveadhesive layer 32 can be a photo-sensitive polymer. The tethers 60 canbe breakable tethers and the transparent intermediate substrate 80 canbe a quartz substrate. The singulated active components 22 can have aprocess side 24 and a different back side 25 opposite the process side24. Connection pads 26 are formed on the process side 24 and the processside 24 is adhered to the patterned photo-sensitive adhesive layer 32. Asingulated active component 22 is an active component 22 that has aseparate substrate and does not share a substrate with any other activecomponent 22. The tethers 60 are not part of an active component 22substrate or the transparent intermediate substrate 80.

As shown in FIGS. 1-9 and as illustrated in the flow diagram of FIG. 16,a method for selectively transferring active components 22 from a sourcesubstrate 20 to an transparent intermediate substrate 80 comprisesproviding a source substrate 20 having a process side 24 and a pluralityof active components 22 formed on or in the process side 24 of thesource substrate 20. A transparent intermediate substrate 80 having apatterned side 84 is provided. A photo-sensitive adhesive layer 30 iscoated on the patterned side 84 of the transparent intermediate wafer80. The patterned side 84 of the transparent intermediate substrate 80is adhered to the process side 24 of the source substrate 20. Portionsof the source substrate 20 are removed, leaving the active components 22adhered to the patterned side 84 of the transparent intermediatesubstrate 80. The photo-sensitive adhesive layer 30 is exposed topatterned electromagnetic radiation 40 to provide differential adhesionin the photo-sensitive adhesive layer 30. Portions of the patternedphoto-sensitive adhesive layer 32 are then selectively removed accordingto the electro-magnetic radiation pattern, thereby forming tethers 60physically connecting the active components 22 to the transparentintermediate substrate 80.

In a further embodiment of the present invention, the active components22 adhered to the transparent intermediate substrate 80 are transferredto a destination substrate 10. Referring to FIG. 19 and FIGS. 14-15described below, a destination substrate 10 having a receiving side 12is provided in step 135 on which the active components 22 are to belocated. The receiving side 12 of the destination substrate 10 can beprocessed and can include a variety of layers and elements, for exampleconductors, connectors, connection pads, solder materials, insulators,or functional elements such as integrated circuits. These receiving sideelements can serve to electrically connect the active components 22 tothe destination substrate 10 and provide power, ground, and controlsignals as desired to make use of the functionality provided by theactive components 22.

Referring to FIG. 10 and step 140 of FIG. 19, a patterned stamp 90 isprovided. The patterned stamp 90 has pillars 92 that can be shaped tomatch the shape of the active components 22. The stamp 90 can be made ofan elastomeric material such as PDMS and the pillars 92 formed usingmethods described in greater detail in the paper “AMOLED Displays usingTransfer-Printed Integrated Circuits” referenced above.

The pillars 92 of the patterned stamp 90 are aligned with the activecomponents 22 adhered to the transparent intermediate substrate 80 asshown in FIG. 11 and referenced in step 145 of FIG. 19. The stamp 90 andpillars 92 are pressed against the active components 22 adhered to thepatterned photo-sensitive adhesive layer 32, the optical mask 82 (ifpresent) and the patterned side 84 of transparent intermediate substrate80, thereby breaking the tethers 60 and adhering the active components22 to the pillars 90, for example with van der Waal's forces. Althougheach active component 22 is illustrated in FIG. 11 pressed against acorresponding pillar 92, in various embodiments of the present inventionfewer pillars 92 may be provided so that only a subset of the activecomponents 22 are removed. Referring to FIG. 12, the broken tethers 62and the transparent intermediate substrate 80 are then removed, leavingthe back side of the active components 22 adhered to the pillars 92 ofthe stamp 90, as shown in FIG. 13. The connection pads 26 of the activecomponents 22 are exposed.

The active components 22 are then adhered to the receiving side 12 ofthe destination substrate 10, as shown in FIG. 14 and referenced in step150 of FIG. 19, by pressing the active components 22 on the stamp 90pillars 92 in alignment to any receiving side 12 structures, elements,or destination receiving side layers 13, for example destinationsubstrate conductive contacts 11. The receiving side 12 can include anadhesive layer, which can be patterned and/or conductive, to adhere theactive components 22 to the destination substrate 10. The stamp 90 isthen removed from the receiving side 12, leaving the transferred activecomponents 22A adhered to the destination substrate 10, as illustratedin FIG. 15.

Other transfer methods can also be used to transfer active components 22from the transparent intermediate substrate 80 to the destinationsubstrate 10. For example, for larger integrated circuit devices,pick-and-place technologies can be employed, such as vacuum adhesion,for either single or multiple die transfer.

In further embodiments of the present invention, referring to FIG. 20,the transparent intermediate substrate 80 can be cleaned in step 155 byremoving any remaining portions of the photo-sensitive adhesive layer 30from the transparent intermediate substrate 80. In other embodiments,the optical mask can also be removed. The transparent intermediatesubstrate 80 can then be reused in step 160 by coating a secondphoto-sensitive adhesive layer 30 on the patterned side 84 of thetransparent intermediate wafer 80 and adhering the process side 24 of asecond source substrate 20 to the patterned side 84 of the transparentintermediate substrate 80 in step 165. Thus, the transparentintermediate substrate 80 can be reused.

Embodiments of the present invention provide advantages over otherprinting methods, for example, as discussed in the paper referencedabove. By employing a transparent intermediate substrate 80, robust andinexpensive processes and materials used in the integrated circuit andphotolithographic industries can be employed to transfer activecomponents 22 from a source substrate 20 to a destination substrate 10.For example, silicon foundry and back-side grinding techniques may bereadily employed. Furthermore, as described above, the methods andtransfer devices of embodiments of the present invention enable theadhesion of the process side 24 and connection pads 26 of the activecomponents 22 adjacent to the receiving side 12 of the destinationsubstrate 10, simplifying electrical connections between the activecomponents 22 and any devices or structures on the destination substrate10 and reducing process steps. Moreover, the transparent intermediatesubstrate 80 can be reused, reducing costs. These processes can also beemployed with flexible destination substrates and substrates that areless tolerant of chemical or high temperature process steps.

The source substrate 20, destination substrate 10, stamp 90, andtransparent intermediate substrate 80 can be made separately, atdifferent times, and/or in different temporal orders or locations andprovided in various process states.

The photo-sensitive adhesive layer 30 can be located on the patternedside 84 of the transparent intermediate substrate 80 (as illustratedFIG. 3), or it can be applied to the active components 22 and processside 24 of the source substrate 20. When the transparent intermediatesubstrate 80 is removed from the active components 22, a portion of thepatterned photo-sensitive adhesive layer 32 and the broken tethers 62can be adhered to the active components 22. The active components 22 canbe cleaned prior to transferring the active components 22 to thereceiving side 12 of the destination substrate 10.

Suitable photo-sensitive adhesive materials, for example UV-curableadhesive resins, are used in the photo-lithographic industry. Adhesivescan be applied, for example, as a film on a carrier that is applied to asubstrate and the carrier can be subsequently removed, for example bypeeling, leaving an adhesive film on the substrate. Additionally oralternatively, uncured liquid adhesives can be coated, for example byspin coating or curtain coating, or other coating methods. Theselectively curable photo-sensitive adhesive layer 30 can also oralternatively be applied to the active components 22 and on the sourcesubstrate 20. A photo-sensitive adhesive, as used herein, is a material(dry or liquid) that can be cured in some areas, but not others, forexample, by the patterned application of photonic energy (e.g.,electromagnetic energy such as ultra-violet radiation or light). A lasercan be used to provide light or heat to selected areas either to enhanceadhesion or to degrade adhesion.

According to various embodiments, a variety of materials can be used forvarious elements in the invention. The selectively curablephoto-sensitive adhesive layer 30 can include materials that improve theabsorption of light or heat, to improve the rate of curing, for exampledyes. The radiation pattern corresponds to the spatial area cured. Awide variety of substrate materials can be employed, for example glass,polymers, quartz, and silicon. In particular, glass substrates are usedin various industries such as display, radiography, and photo-voltaics.A variety of active components 22 may be used, for example, such asactive components formed in layers of silicon. In one embodiment of anactive component 22, thin-film transistors are photo-lithographicallyformed on a thin silicon layer sputtered and possibly processed on aglass substrate. However, such active components 22 typically have lowerperformance and are mechanically fragile, which may lead to damageduring the transfer process and can lack adequate mechanical robustness.

In some embodiments, the active components 22 are small integratedcircuits formed in a semiconductor wafer source substrate 20, forexample gallium arsenide or silicon, which can have a crystallinestructure. Processing technologies for these materials typically employhigh heat and reactive chemicals. However, by employing transfertechnologies that do not stress the active component 22 or substratematerials, more benign environmental conditions can be used as comparedto thin-film manufacturing processes. Thus, embodiments of the presentinvention provide advantages in that flexible substrates that aretypically intolerant of extreme processing conditions (e.g. heat,chemical, or mechanical processes) can be employed as the destinationsubstrates 10. Furthermore, it has been demonstrated that crystallinesilicon substrates have strong mechanical properties and, in smallsizes, can be relatively flexible and tolerant of mechanical stress.This is particularly true for substrates of about 5 micron, 10 micron,20 micron, 50 micron, or even 100-micron thicknesses. Additionally oralternatively, the active components 22 can be formed in amicrocrystalline, polycrystalline, or amorphous semiconductor layer.

The active components 22 can be constructed using foundry fabricationprocesses. Layers of materials can be used, including materials such asmetals, oxides, nitrides and other materials used in theintegrated-circuit art. Each active component 22 can be a completesemiconductor integrated circuit and can include, for example,transistors. The active components 22 can have different sizes, forexample, about 1000 square microns or about 10,000 square microns, about100,000 square microns, or about 1 square mm, or larger, and can havevariable aspect ratios, for example about 1:1, 2:1, 5:1, or 10:1. Theactive components 22 can be rectangular or can have other shapes.

The stamp 90 can be flat or structured, for example with pillars 92matched to the shapes, sizes, and locations of the active components 22to enhance adhesion. The stamp 90 can be elastomeric, for example madeof PDMS, rubber, or a reinforced composite.

The adhesion between the active components 22 and the receiving side 12of the destination substrate 10 should be greater than the adhesionbetween the active components 22 and the stamp 90. When the stamp 90 isremoved from the receiving side 12 of the destination substrate 10, theactive components 22 must adhere more strongly to the receiving side 12than to the stamp 90, in order to transfer the active components 22 fromthe stamp 90 to the receiving side 12 of the destination substrate 10.

In one embodiment of the method, the stamp 90 adheres only a subset ofthe active components 22, for example a subset array of the availableactive components 22 on the transparent intermediate substrate 80.Subsequent stamping steps can then remove different subset arrays ofactive components 22 from the transparent intermediate substrate 80 andstamp them in different locations on the destination substrate 10 toform a sparse array of active components 22 adhered to the receivingside 12 of the destination substrate 10.

In other embodiments, all of the active components 22 within an array onthe transparent intermediate wafer 80 are removed from the transparentintermediate wafer 80 and adhered to the stamp 90. Likewise, all of theremoved active components 22 are stamped onto the receiving side 12 ofthe destination substrate 10. However, only selected active components22, for example a subset array of the active components 22 on the stamp90 are adhered to the destination substrate 10 by selectively curingareas of an adhesive layer formed on the receiving side 12 andcorresponding to the selected active components 22. The stamp 90 is thenremoved from the destination substrate 10 and can be reapplied elsewhereon the destination substrate 10 to selectively adhere another differentsubset array of active components 22 to another different destinationsubstrate area. In this embodiment, there is no need to repeatedly pressthe stamp 90 against the transparent intermediate wafer 80, but theadhesion of the active components 22 to the stamp 90 must be strongerthan the uncured adhesion to the destination substrate 10 and weakerthan the cured adhesion to the destination substrate 10.

Referring to the flow diagrams of FIGS. 16 and 20, the methods ofembodiments of the present invention can be iteratively applied to asingle or multiple destination substrates 10. By repeatedly transferringsub-arrays of active components 22 from a stamp 90 to a destinationsubstrate 10 and relatively or laterally moving the stamp 90 anddestination substrates 10 between stamping operations a distance equalto the spacing of the selected active components 22 in the transferredsub-array between each transfer of active components 22, an array ofactive components 22 formed at a high density on a source substrate 20can be transferred to a destination substrate 10 at a lower density. Inpractice, the source substrate 20 is likely to be expensive, and formingactive components 22 with a high density on the source substrate 20 canreduce the cost of the active components 22, especially as compared toforming active components on the destination substrate 10. Transferringthe active components 22 to a lower-density destination substrate 10 canbe used, for example, if the active components 22 manage elementsdistributed over the destination substrate 10, for example in a display,digital radiographic plate, or photovoltaic system.

In particular, in the case wherein the active component 22 is anintegrated circuit formed in a crystalline semiconductor material, theintegrated circuit substrate provides sufficient cohesion, strength, andflexibility that it can adhere to the destination substrate 10 withoutbreaking as the stamp 90 is removed.

In various methods of the present invention, laser beams are used toselectively cure selected adhesive areas. In one embodiment, theselected areas can be sequentially exposed. In another embodiment,multiple areas can be simultaneously exposed, thereby increasing thenumber of selected active components simultaneously adhered. Suchselective exposure can enable the selection of known good die, byensuring that only tethers associated with known good die are patternedfor transfer. Thus, methods of the present invention include selectivelyexposing the photo-sensitive adhesive layer 30 to differentially adhereactive components 22 to the transparent intermediate substrate 80. Themethod can further include selectively exposing the photo-sensitiveadhesive layer 30 to differentially adhere electrically defective activecomponents. Selective adhesion of the active components 22 can beaccomplished by controlling the size of the tethers 60 or by adheringthe active components 22 itself to the transparent intermediatesubstrate 80 or to the source substrate 20. Active components 22 can betested while still on the source substrate 20. In this way, activecomponents 22 known to be defective can be prevented from beingtransferred from one substrate to another substrate.

Other methods employing a mask can also adhere multiple selected activecomponents at one time. Methods for scanning and controlling lasers canbe employed, as well as light sources used in conjunction with alignedmasks, particularly as are used in the photo-lithographic arts.

In comparison to thin-film manufacturing methods, using denselypopulated source substrates 20 and transferring active components 22 toa destination substrate 10 that requires only a sparse array of activecomponents 22 located thereon does not waste or require active layermaterial on a destination substrate 10. Embodiments of the presentinvention may also be used in transferring active components 22 madewith crystalline semiconductor materials that have higher performancethan thin-film active components. Furthermore, the flatness, smoothness,chemical stability, and heat stability requirements for a destinationsubstrate 10 used in embodiments of the present invention are reducedbecause the adhesion and transfer process is not significantly limitedby the destination substrate material properties. Manufacturing andmaterial costs may be reduced because of high utilization rates ofexpensive materials (e.g. the source substrate) and reduced material andprocessing requirements for the destination substrate.

Many different embodiments have been disclosed herein, in connectionwith the above description and the drawings. It will be understood thatit would be unduly repetitious and obfuscating to literally describe andillustrate every combination and subcombination of these embodiments.Accordingly, the present specification, including the drawings, shall beconstrued to constitute a complete written description of allcombinations and subcombinations of the embodiments described herein,and of the manner and process of making and using them, and shallsupport claims to any such combination or subcombination.

In the specification, there have been disclosed embodiments of theinvention and, although specific terms are employed, they are used in ageneric and descriptive sense only and not for purposes of limitation.The following claims are provided to ensure that the present applicationmeets all statutory requirements as a priority application in alljurisdictions and shall not be construed as setting forth the scope ofthe present invention.

That which is claimed:
 1. A method of printing transferable components,the method comprising: forming a photo-sensitive adhesive layer on aprocess side of a source substrate including active components or on apatterned side of a transparent intermediate substrate; contacting thetransparent intermediate substrate with the source substrate to adherethe active components on the process side to the patterned side of thetransparent intermediate substrate via the photo-sensitive adhesivelayer therebetween; removing portions of the source substrate oppositethe process side to singulate the active components; selectivelyexposing portions of the photo-sensitive adhesive layer toelectromagnetic radiation through the transparent intermediate substrateto alter an adhesive strength thereof; and then selectively removingportions of the photo-sensitive adhesive layer having a weaker adhesivestrength to define breakable tethers comprising portions of the adhesivelayer having a stronger adhesive strength, wherein the breakable tethersphysically secure the active components to the transparent intermediatesubstrate.
 2. The method of claim 1, wherein selectively exposingcomprises: forming a mask pattern on the transparent intermediatesubstrate; and exposing the transparent intermediate substrate to theelectromagnetic radiation, wherein the mask pattern comprises a materialconfigured to block transmission of the electromagnetic radiationtherethrough such that the portions of the photo-sensitive adhesivelayer exposed by the mask pattern are selectively exposed to theelectromagnetic radiation.
 3. The method of claim 2, wherein thepatterned side of the transparent intermediate substrate includes aplurality of structures protruding therefrom, and wherein the maskpattern is formed on surfaces of the protruding structures.
 4. Themethod of claim 1, wherein the tethers extend in a directionperpendicular to the transparent intermediate layer and are shaped tobreak in a desired manner.
 5. The method of claim 1, wherein the activecomponents have respective primary surfaces including conductiveelements thereon adjacent the process side of the source substrate andrespective secondary surfaces opposite the primary surfaces, and whereinthe portions of the adhesive layer defining the tethers physicallyconnect the respective the primary surfaces of the active components tothe transparent intermediate substrate.
 6. The method of claim 5,further comprising: pressing a stamp having pillars protruding therefromagainst the active components on the transparent intermediate substrateand separating the stamp from the transparent intermediate substrate tobreak the tethers and adhere the respective secondary surfaces of theactive components to respective transfer surfaces of the pillars of thestamp; and contacting the stamp including the active components on thepillars thereof with a destination substrate to adhere the respectiveprimary surfaces of the active components including the conductiveelements thereon to a receiving surface of the destination substrate. 7.The method of claim 6, wherein the conductive elements on the respectiveprimary surfaces of the active components are adhered to respectiveelectrical contacts on the receiving surface of the destinationsubstrate.
 8. The method of claim 6, wherein the primary surfaces of theactive components respectively include a photo-adhesive layer residuethereon comprising respective portions of the breakable tethers, whereinthe residue is below respective surfaces of the conductive elements. 9.The method of claim 1, wherein selectively exposing comprises:selectively exposing the portions of the photo-sensitive adhesive layerto differentially adhere ones of the active components to thetransparent intermediate substrate.
 10. The method of claim 1, furthercomprising: providing the source substrate having the process side andthe active components adjacent the process side of the source substrate;providing the transparent intermediate substrate having the patternedside; providing the photo-sensitive adhesive layer on the patterned sideof the transparent intermediate wafer or on the active components;adhering the patterned side of the transparent intermediate substrate tothe process side of the source substrate via the photo-sensitiveadhesive layer; removing the portions of the source substrate tosingulate the active components and adhere the singulated activecomponents to the patterned side of the transparent intermediatesubstrate; selectively exposing the photo-sensitive adhesive layer tothe electromagnetic radiation to alter the adhesive strength thereofsuch that the portions of the photo-sensitive adhesive layer have aweaker adhesive strength than other portions thereof; and selectivelyremoving the portions of the photo-sensitive adhesive layer having theweaker adhesive strength to define the breakable tethers comprising theother portions of the photo-sensitive adhesive layer that physicallyconnect the singulated active components to the transparent intermediatesubstrate.
 11. The method of claim 10, further including forming anoptical mask on the patterned side of the transparent intermediatesubstrate and selectively exposing the photo-sensitive adhesive layer toelectromagnetic radiation through the optical mask.
 12. The method ofclaim 10, further including selectively exposing the photo-sensitiveadhesive layer to electromagnetic radiation with a patterned laser beam.13. The method of claim 12, further including selectively exposing thephoto-sensitive adhesive layer to differentially adhere ones of theactive components.
 14. The method of claim 13, further includingselectively exposing the photo-sensitive adhesive layer todifferentially adhere electrically defective ones of the activecomponents.
 15. The method of claim 10, further including: providing adestination substrate having a receiving side; providing a patternedstamp having a plurality of pillars, each pillar spatially correspondingto an active component; pressing the stamp pillars against the activecomponents to detach the active components from the transparentintermediate substrate, thereby adhering the active components to thestamp pillars; and pressing the active components against the receivingside of the destination substrate with the stamp to adhere the activecomponents to the destination substrate.
 16. The method of claim 15,further including: removing remaining portions of the photo-sensitiveadhesive layer from the transparent intermediate substrate.
 17. Themethod of claim 16, further including: coating a second photo-sensitiveadhesive layer on the patterned side of the transparent intermediatewafer; and adhering the process side of a second source substrate to thepatterned side of the transparent intermediate substrate.
 18. The methodof claim 15, further including breaking the tethers.
 19. The method ofclaim 10, further including providing a source substrate that is asemiconductor wafer, a silicon wafer, or a gallium arsenide wafer. 20.The method of claim 10, further including providing active componentsthat include a crystalline, a microcrystalline, a polycrystalline, or anamorphous semiconductor material.
 21. The method of claim 10, furtherincluding first removing the majority of the source substrate in a firststep and removing a minority of the source substrate in a second stepdifferent from the first step.
 22. The method of claim 21, furtherincluding removing a portion of the source substrate before thetransparent intermediate substrate is adhered to the source substrate.23. The method of claim 10, further including exposing thephoto-sensitive adhesive layer to patterned electromagnetic radiationbefore the source substrate is adhered to the transparent intermediatesubstrate, after the source substrate is adhered to the transparentintermediate substrate, after portions of the source substrate areremoved, or after a first portion of the source substrate is removed butbefore a second portion of the source substrate is removed.
 24. Themethod of claim 10, further including grinding or etching back thesource substrate leaving the active components on the process sideadhered to the patterned side of the transparent intermediate substrate.25. The method of claim 10, wherein the tethers physically connect theactive components in a component layer to the transparent intermediatesubstrate in a substrate layer, wherein the tethers are formed in atether layer that is between the component layer and the substratelayer, and wherein the component layer, the tether layer, and thesubstrate layer are all different layers.
 26. The method of claim 10,further including coating the photosensitive adhesive layer from anadhesive carrier.
 27. The method of claim 10, further includingproviding a transparent intermediate substrate with protrudingstructures on the patterned side.
 28. The method of claim 10, furtherincluding using chemical processes or laser ablation to shape thetethers.